C. difficile infections have doubled in recent years, and one epidemic strain has caused severe outbreaks in hospitals and long-term care facilities, where the infection is most common. About 300,000 to 500,000 Americans contract C. difficile infections each year, and recurrences are common.

"Treatment of patients with C. difficile with two novel antibodies resulted in a 72% reduction in the number of patients that would recur with that disease," said lead researcher Dr. Donna Ambrosino, executive director of MassBiologics, the company that developed the monoclonal antibodies, and a professor of pediatrics at the University of Massachusetts Medical School.

The report was published in the Jan. 21 issue of the New England Journal of Medicine.

"The biggest issue beyond the initial disease is that even though [people] get better from the initial disease, they go on to have recurrences, and this treatment is preventing those recurrences," she explained.

C. difficile, which settles in the gastrointestinal tract, often strikes people receiving prolonged antibiotic treatment for other infections. It can cause severe diarrhea and damage the lining of the large intestine.

Treatment usually involves antibiotics, which also wipe out normal bowel flora, according to an accompanying editorial in the journal.

After antibiotic treatment, two toxins remain in the body that can cause a relapse. Moreover, the toxins resulting from the epidemic strain appear to cause more severe illness, a higher rate of relapse and about 7% mortality, Ambrosino said.

"The toxins are more of a problem than the actual bacteria," said Dr. Marc Siegel, an associate professor of medicine at NYU Langone Medical Center in New York City.

The two new monoclonal antibodies -- antibodies that are cloned in the laboratory from a single hybrid cell -- are designed to remove both toxins, thereby preventing a recurrence.

In this phase II trial, Ambrosino's group randomly assigned 200 patients with C. difficile infection to antibiotic treatment with either vancomycin or metronidazole plus injections of two monoclonal antibodies or placebo.

After 84 days, recurrence of C. difficile occurred in 7% of the patients who received the monoclonal antibodies, compared with 25% of those given placebo, the researchers found.

In addition, only 8% of the patients with the epidemic strain of C. difficile who were given the antibodies suffered a relapse compared with 32% of the placebo group.

"We hope that this new treatment offers hope to these patients in ultimately reducing the health care burden and hospitalizations," Ambrosino said. "Now a larger number of patients will be studied to get the final approval," she added.

Siegel applauded the researchers' work. "The idea of monoclonal antibodies to target the toxins while at the same time killing the bacteria is a tremendous therapeutic approach," he said. "It is very likely to be successful and this study is convincing."

More study is needed on potential side effects from this treatment, Siegel noted. "But this is very promising and it is the wave of the future in treatments," he added.